Overview
The rubric states that the priest and deacon who wish to celebrate the Divine Liturgy, must be free of moral sin, continent, and must fast from the night before. In addition, they are required to have performed the devotions required by the Eucharistic discipline and have celebrated (or at least attended) Vespers and Matins for that day. They should keep themselves in a state of spiritual calm and reverence as they prepare to celebrate the Sacred Mysteries.
When it comes time for the service, the priest and deacon enter the temple, clothed in choir dress: podryasnik (inner cassock) and riassa (outer cassock). If they are monks they wear klobuks and mandyas; if either of them has been granted the kamilavka he wears it. If the priest has been granted the pectoral cross he wears it.
After venerating the icon in the narthex they enter the nave and make three metanias (bows at the waist) or prostrations, depending upon the day. They may venerate other icons in the nave, and then they proceed to the front of the temple and stand just in front of the ambon (an elevated area in front of the Holy Doors of the Iconostasis). There they make three more metanias, the priest gives the opening blessing, "Blessed is our God, always, now and ever, and unto the ages of ages." The deacon responds, "Amen", and continues with the usual beginning (a series of prayers which includes the Trisagion and the Lord's Prayer).
At the conclusion of the usual beginning, the priest and deacon step up onto the ambon and venerate the icons of Christ and the Theotokos (Virgin Mary). For this purpose, there are often smaller "kissing icons" hung on doorposts of Holy Doors (on the picture above, they can be seen as two small gold squares to either side of the Holy Doors). If there are no "kissing icons" they will venerate the major icons of Christ and the Theotokos on the Iconostasis. As they venerate the icon of Christ, the deacon says the following troparion:
We venerate Thy most pure icon, O Pure One, asking the forgiveness of our transgressions, O Christ God. For of Thine own will Thou was well-pleased to ascend the Cross, that Thou mightest deliver from bondage to the enemy them whom Thou didst fashion. Wherefore, we cry to The thankfully: Thou didst fill all things with joy, O our Saviour, when Thou camest to save the world.
As they venerate the icon of the Theotokos, the deacon says:
O Theotokos, in that thou art a well-spring of loving-kindness, vouchsafe unto us thy compassion. Look upon the people who have sinned. Manifest thy power as ever; for trusting in thee we cry aloud unto thee: Hail! as afforetime did Gabriel, Chief Captain of the Bodiless Powers.
The priest then removes his klobuk or kamilavka, bows his head, and gesturing with his right hand towards the Holy Doors, he says:
Stretch forth Thy hand, O Lord, from thy holy dwelling-place on high, and strengthen me for this, Thine appointed service; that standing uncondemned before Thy dread Thone, I may fulfill the sacred, bloodless sacrifice.
They then make three metanias in front of the Holy Doors, bow to each other, and then to either side of the nave and enter the altar (sanctuary) by the two side doors ("Deacon's Doors") of the iconostasis.
Then, standing in front of the Holy Table (altar table) they venerate it, making prostrations if it is a weekday, or metanias if it is Sunday. The priest kisses the Gospel Book and the front edge of the Holy Table, the deacon kisses the blessing cross and the right (south) edge of the Holy Table. The deacon then receives the priest's blessing and they both say their vesting prayers, put on their sacred vestments, and begin the Liturgy of Preparation during which the bread and wine are prepared for the Eucharist. About half an hour before the Liturgy is scheduled to begin, the priest gives the blessing for the Little Hours (normally the Third Hour and Sixth Hour) to begin.
Read more about this topic: Entrance Prayers